General support for Outlook 2007 will end on April 10, 2012.
Outlook 2007 Security Fixes Through 2017
That means security updates will be available free from Windows Update until April 11, 2017. Other new updates such as service packs and hotfixes can be downloaded at least until April 10, 2012.
Paid phone support for Outlook 2007 and updates to the Microsoft Knowledge Base will be available through April 11, 2017.